diff --git a/test/testUtils/mocks/mocksContainer/mockContainer.ts b/test/testUtils/mocks/mocksContainer/mockContainer.ts
index b392e61f9f7..883c3856c26 100644
--- a/test/testUtils/mocks/mocksContainer/mockContainer.ts
+++ b/test/testUtils/mocks/mocksContainer/mockContainer.ts
@@ -214,9 +214,12 @@ export default class MockContainer implements MockGameObject {
     return this;
   }
 
-  add(...obj: MockGameObject[]): this {
-    // Adds a child to this Game Object.
-    this.list.push(...obj);
+  add(obj: MockGameObject | MockGameObject[]): this {
+    if (Array.isArray(obj)) {
+      this.list.push(...obj);
+    } else {
+      this.list.push(obj);
+    }
     return this;
   }
 
diff --git a/test/testUtils/mocks/mocksContainer/mockRectangle.ts b/test/testUtils/mocks/mocksContainer/mockRectangle.ts
index f9a92c41904..c11af824c56 100644
--- a/test/testUtils/mocks/mocksContainer/mockRectangle.ts
+++ b/test/testUtils/mocks/mocksContainer/mockRectangle.ts
@@ -47,9 +47,13 @@ export default class MockRectangle implements MockGameObject {
     this.list = [];
   }
 
-  add(obj): this {
+  add(obj: MockGameObject | MockGameObject[]): this {
     // Adds a child to this Game Object.
-    this.list.push(obj);
+    if (Array.isArray(obj)) {
+      this.list.push(...obj);
+    } else {
+      this.list.push(obj);
+    }
     return this;
   }
 
diff --git a/test/testUtils/mocks/mocksContainer/mockSprite.ts b/test/testUtils/mocks/mocksContainer/mockSprite.ts
index b8ccfcced1f..ad70b6ced07 100644
--- a/test/testUtils/mocks/mocksContainer/mockSprite.ts
+++ b/test/testUtils/mocks/mocksContainer/mockSprite.ts
@@ -201,9 +201,13 @@ export default class MockSprite implements MockGameObject {
     return this;
   }
 
-  add(obj): this {
+  add(obj: MockGameObject | MockGameObject[]): this {
     // Adds a child to this Game Object.
-    this.list.push(obj);
+    if (Array.isArray(obj)) {
+      this.list.push(...obj);
+    } else {
+      this.list.push(obj);
+    }
     return this;
   }